This proposal for the Phase 2 Faculty Transition of a mentored research career development award will provide the candidate with the broad knowledge in the design and conduct of research in innate immunity and will lead to her successful transition to an independent researcher. The proposal builds on experience of the candidate in oral microbiology and in the interaction of oral bacteria with epithelial cells in innate defense. The hypothesis to be tested is that commensal and pathogenic bacteria utilize different signaling pathways in inducing human beta-defensins, antimicrobial peptides that are components of the innate immune response. This work will focus on the distinctive pathways and receptors utilized by commensal and pathogenic organisms from oral mucosa and skin. Preliminary data indicate that commensal bacteria use MAPK pathways, whereas pathogens use both MAPK and NFkappaB in inducing human beta-defensin-2 (hBD-2). RNAi technology will be utilized to differentiate the two arms of the NFkappaB pathway and to investigate receptors and other signaling pathway components involved in human a-defensin induction. This proposal will also investigate virulence factors of Porphyromonas gingivalis, an aggressive periodontal pathogen, involved in human beta-defensin induction, and identify signaling pathways involved. The studies of this proposal will lead to a better understanding of the way epithelial cells respond differently to pathogenic and commensal organisms. This work will help define the manner in which epithelial cells can distinguish commensals and pathogens and produce individualized responses, and how different cell-surface receptors interact with different bacteria and signal human beta-defensin induction. This is an important aspect of the innate immune response that has not been previously investigated. By using cells and bacterial species from two different body sites, the conclusions will be broader and more generally significant. Identifying specific routes pathogens take in stimulating beta-defensins may open the way for development of new therapeutic agents that stimulate the innate immune response.